Arc interrupting composition and apparatus

ABSTRACT

An arc interrupting composition for the arc-exposure walls or surfaces of electric circuit interrupting devices. The composition comprises a combination of hydrated alumina and melamine in a binder which may be a thermosetting resin but is preferably a thermoplastic resin which is more reactive to arcing than the melamine. Under arcing conditions, it is believed the binder vaporizes or decomposes violently and the hydrated alumina gives off water of hydration, and that these effects interact to render the melamine more effective and to create improved arc interruption conditions and service life.

United States Patent [191 Jones ARC INTERRUPTING COMPOSITION ANDAPPARATUS [75] Inventor: Paul W. Jones, Lafayette, Ind. [73] Assignee:Rostone Corporation, Lafayette, Ind. [22] Filed: Oct. 20, 1972 [21]Apple No.: 299,431

Related US. Application Data [63] Continuation-impart of Ser. No.59,554, July 30,

1970, abandoned.

[52] US. Cl. ZOO/I44 C, 200/149 A [51] Int. Cl. H0lh 33/04 [58] Field ofSearch 200/144 C, 149 A, 200/149 R, 144 R [56] References Cited UNITEDSTATES PATENTS 2,526,448 10/1950 Amundson et al 200/149 A 2,768,26410/1956 Jones et a1. 200/144 C 3.242257 3/1966 Jones et a1. 200/144 C[111 3,761,660 1 Sept. 25, 1973 3,582,586 6/1971 Jones 200/144 C FOREIGNPATENTS OR APPLICATIONS 1,065,914 11/1958 Germany 200/144 C PrimaryExaminerRobert S. Macon AttorneyThomas P. Jenkins et a1.

[57] ABSTRACT An arc interrupting composition for the arc-exposure wallsor surfaces of electric circuit interrupting devices. The compositioncomprises a combination of hydrated alumina and melamine in a binderwhich may be a thermosetting resin but is preferably a thermoplasticresin which is more reactive to arcing than the melamine. Under arcingconditions, it is believed the binder vaporizes or decomposes violentlyand the hydrated alumina gives off water of hydration, and that theseeffects interact to render the melamine more effective and to createimproved arc interruption conditions and service life.

6 Claims, 7 Drawing Figures PATENTED SEP25 I975 sum 10F 2 ARCINTERRUPTING COMPOSITION AND APPARATUS This application is acontinuation-in-part of my prior copending application Ser. No. 59,554,filed July 30, 1970, now abandoned which discloses certain subjectmatter which was previously disclosed in my prior copending applicationSer. No. 536,119, filed Mar. 21, 1966, for Arc-lnterrupting Materialsand Apparatus, now U.S. Pat. No. 3,582,586.

BACKGROUND OF THE INVENTION This invention relates to arc-interruptingcompositions especially adapted for use at the arc-exposure walls andsurfaces, i.e., those exposed to-arcing, in electriccircuit-interrupting apparatus, to improve the circuit interruptingcharacteristics of such apparatus.

US. Pat. No. 2,768,264 to myself and Robert E. Wilkinson discloses theuse of hydrated alumina in molded electrical insulating elements toprovide both good physical strength and good electrical properties,especially to provide advantageous arc suppressing and arc quenchingcharacteristics and to reduce the tendency of organic substances tocarbonize on the surface of the material and form a conductive path,that is, to prevent so-called carbon tracking. US. Pat. No.3,242,257 tothe same patentees discloses the use of certain addition compoundsproviding electronegativeelements in the composition to improve theionization conditions produced by such hydrated alumina compositions.The use of hydrated alumina in electrical apparatus as disclosed inthese prior patents has become wide spread and has been responsible forgreat improvements in electrical apparatus, for example, in reducing thesize and increasing the capacity of switching apparatus and variousother circuit interrupting de vices. The role and action of hydratedalumina to give its improved results has been investigated by severalinvestigators and has been attributed both to its release of water ofhydration for effective are quenching and to its catalyzing theoxidation of carbonaceous material and thereby preventing carbondeposits on arcexposure surfaces.

The arc-quenching abilities of hydrated alumina compositions andothermaterials has not, however, satisfied the demand for even betterarc controlling means, arising both from the use of electrical circuitsat higher voltage and amperages, and from economic requirements forgreater performance and safety at less cost. This is an empirical art,dealing with the violent and variable conditions of electrical arcing.Hydrated alumina compositions seemed to have reached the limit of theirperformance capabilities.

My prior co-pending application, now U.S. Pat. No. 3,582,586, proposedare interrupting compositions of a different character, and sought toprovide effective are interruption under performance conditions, such asat high voltage and amperage, where hydrated alumina compositions werenot adequately effective. Such application proposed-compositionsconsisting of (l) the chemical compound melamine, which is effective asan arc interrupting material for very high power arcs but is not highlyeffective at lower power conditions, and particularly not at lowcurrents, and (2) a thermoplastic binder which is substantially morevolatile and more unstable than the melamine and which in the presenceof an arc would rapidly volatilze or decompose to form a large volume ofgas and to propel the melamine with explosive force into the core of thearc to render the melamine more effective under a wide range ofconditions.

The present application is based on the discovery that whereasthehydrated alumina-based compositions and the melamine-basedcompositions were each limited in their arc-interruptingcharacteristics, particularly in some ranges of voltage and amperageconditions, the combination of both melamine and hydrated alumina asessential components with a binder in a single composition givesremarkably improved results over those obtainable with compositionsbased on either hydrated alumina or melamine alone.

' The reason and explanation for this improvement is not clear, and runscounter to what might be expected. Thus the hydrated alumina has beenconsidered to be effective because of the cooling effect of its releaseof water of hydration, whereas the melamine composition of my priorco-pending application could be considered effective because of theeffect of the binder in producing more effective heating of themelamine. It is thought that the improvement involves a change in theionization conditions in the are as a result of interaction ofthemelamine and the hydrated alumina.

In addition to the melamine, hydrated alumina, and binder, thecomposition may contain other conventional fillers and the like, and maycontain reinforcing fibers such as glass fiber, asbestos, and the like.The

composition may also contain addition agents in accordance with theteachings of US. Pat. No. 3,242,257 issued to me jointly with Robert E.Wilkinson and copending with my said application Ser. No. 536,119.

One of the essential components of the composition is melamine, which isa chemical compunnd having the empirical formula C N,,I-l and whichoccurs as a white crystaline powder having a melting point ofapproximately 350 C., but which sublimes at melting temperature andbelow. Its molecule is relatively large and stable, and I believe theseproperties contribute to its arcinterrupting characteristics. It hasbeen proposed in the prior art as an arc-interrupting compound, as inAmundson et al. US. Pat. No. 2,526,448. Melamine itself, however, has anumber of deficiencies, notably its lack of effect at lower powerconditions and its extreme structural weakness which prevents it frombeing molded or pressed in a satisfactory structural shape.

The second essential component of the composition is hydrated alumina,which is considered to have the formula Al O -3H O. This is alsoobtainable as a finely divided dry material which can be mixed in drystate with the melamine.

The binder used in the composition is preferably a thermoplastic resin.Polyethylene resin is especially satisfactory and desirable, since it isobtainable in a finely divided dry state which can be thoroughly anduniforrnly mixed with the other dry components to form a dry mixturewhich can be charged directly as such to molding apparatus. Otherthermoplastic resins which may be used as binders include thepolypropylene, polytetrafluoroethylene, acrylic and acetyl resinsmentioned in my copending application. Other thermoplastic binders whichI consider suitable include vinyl polymers, styrene polymers, cellulosepolymers, polyamides, and polyimides.

Thermoplastic binders are desirable in that they volatilize or decomposeviolently in the presence of an electric arc over a wide range of arcingconditions, especially under low power conditions below those at whichmelamine itself is effective. The effect of the combination of suchbinders in a composition with melamine may be visualized as one in whichthe more responsive binder drives the melamine violently into the verycore of the arc where melamine becomes effective, and one in which thecombination of components produces large volumes of gas both for itsexpulsion effects and for its arc extinguishing effects under all of awide range of conditions.

In addition, thermoplastic binders are advantageous in the compositionwith melamine and hydrated alumina to provide convenient moldingproperties, and to give with such other components a structure ofadequate physical strength, physical and chemical stability, electricalinsulating properties, etc. The choice and proportion of such bindersmay be varied to suit the application for which the composition isintended. Preferably, the binder may be selected for its ownarcinterrupting properties. However, both the melamine and the hydratedalumina in the composition provide effective arc quenching properties,and the hydrated alumina provides non-carbonizing properties, so thatthe binder itself need not necessarily have good arcquenching propertiesor non-carbonizing characteristics.

Whereas the thermoplastic binders are preferable for the reasonsindicated, especially for their interaction with the melamine to enhancethe arc quenching effects of the melamine, the hydrated alumina in thepresence of the arc also appears to interact with the melamine to makeit more effective, so that for at least some applications, various otherorganic binders may be used and may be found desirable. Such otherorganic binders which may be used comprise various known thermosettingresins, including amino resins such as melamine-formaldehyde resin andureaformaldehyde resin, epoxy resins, polyester resins, and phenolicresins. They may also include rubber-like compounds, such as butyl andother synthetic elastomer.

The proportions of the essential compounds of the composition may vary,depending on the application and the arcing conditions to becontrolled.The binder is preferably present in an amount from to 50 percent of thetotal composition. All proportions are by weight.

On the basis of present information, I prefer to use melamine andhydrated alumina in a'combined amount at least equal to the amount ofbinder, and not more than 90 percent and desirably not more than 80percent of the combined total of said components and the binder, and atleast about 25 percent of the total composition. I have found that incombination with melamine and binder, even very small amounts, forexample, l or 2 percent of hydrated alumina is effective to produceimproved arc interrupting results. In each 100 parts by weight of theessential components melamine, hydrated alumina and binder, the bindershould constitute from 10 parts to 50 parts, melamine desirablyconstitutes from 10 parts up to about 80 parts, and hydrated alumina iseffective and desirably present in a range of from about one (1) part upto about 70 parts.

When fillers and like other components are used in the composition, theymay be used in amounts up to say 50 percent of the total composition.

To improve operation at extremely high voltages and amperages, thecomposition may desirably contain a proportion of finely dividedinorganic fillers such as silica, SiO or aluminum fluoride, AL F It isthought that these act to physically absorb heat when projected into thearc, and also, by their vaporization, to remove considerable energy fromthe arc. Under repeated operation, however, these tend to build up fusedor sintered residues, and hence should be avoided in devices where theparts are required to slide on one another or on other parts.

The compositions are used at surfaces which are exposed to arcing incircuit interrupting apparatus. They may be used to mold electricalinsulating elements which forms parts of the apparatus, and the moldingsmay carry inserts forming contacts or mechanical parts of the apparatus.Also, the composition may be formed as inserts in structural parts madeof other material, so that they serve only for are interrupting purposesand hence are placed as arc chutes or wall liners where they confine andare directly exposed to the arcs which occur. Such inserts may be moldedor fabricated as separate parts, or may be formed of composition moldedin place on or in a previously formed part. Also, the compositions maybe applied as surface coatings, as by formulating the composition with abinder in liquid state and applying such composition as a paint-likecoating.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustratethe invention. In such drawings:

FIG. 1 is a longitudinal sectional view of an expulsion type fusecontaining a liner made of a composition in accordance with myinvention;

FIG. 2 is an isometric view of a bayonet-type circuit interrupter havinga liner made of a composition embodying my invention;

FIG. 3 is a diagrammatic view of a testing device for evaluating arcinterrupting compositions of the type here involved;

FIG. 4 is a diagrammatic vertical section of a circuit interruptingswitch which may be considered to represent either one pole" of a switchsuch as that shown in FIG. 1 of prior U.S. Pat. No. 2,768,264 or torepresent a testing device for evaluating compositions in accordancewith the invention;

FIG. 5 is a section on the line 55 of FIG. 4;

FIG. 6 is a graph of the results of tests conducted on a device as shownin FIGS. 4 and 5; and

FIG. 7 is a diagrammatic view of test apparatus used in Example III.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The expulsion-type fuseshown in FIG. 1 is adapted for use in a conventional manner in aconventional fuse carrier. It comprises an outer rigid tube 10 which maybe of conventional vulcanized horne fiber, or a glassreinforced moldedtube, or other known type of expulsion-type fuse tube. At its upper endit carries a terminal collar 12 secured to the tube 10 by a pair of pins14 and having an externally threaded upper end 16 for the reception of acap 18. Adjacent its lower end it carries a terminal clamp 20. The fusecomprises an upper headed fuse terminal 22 adapted to be removablyclamped between the collar terminal 14 and the cap 18, and connected tothe upper end of a strain wire 24 and a fuse wire 26. The lower ends ofthe strain wireand fuse wire are connected to a lower terminal 28 whichis connected by a flexible conductor 30 to the clamp terminal 20 at thelower end of the tube. The fuse is surrounded by a liner 32 which at itsupper end is secured and sealed to the body of the upper fuse terminal22 and which extends as a liner inside the fuse tube for the entirelength of the fuse wire 26 and for a distance beyond the lower fuseterminal 28. The liner is composed of an arc-interrupting composition inaccordance with the present invention.

In operation, when the fuse blows, an arc is formed between the upperfuse terminal 22 and the lower fuse terminal 28, and such arc is closelyconfined and surrounded by the walls of the arc extinguishing liner 32.The are vaporizes the metal of the fuse wire 26 and strain wire 24 andcauses the surface of the liner 32 to vaporize or break down with arapid evolution of gases which expel the terminal 28 and the now freeend of the flexible conductor 30 out of the fuse tube. This lengthensthe arc path, and the gases act to extinguish the lengthened arc. Torenew the fuse, the cap 18 is removed, the fuse terminal 22 and liner 32are withdrawn from the supporting outer tube 10, and a new fuse assemblyand liner 32 are inserted and locked in place by the cap. The conductor30 of the spent fuse is discarded and that of the new fuse assembly isconnected to the clamp 20. Since the liner 32 is physically supported bythe rigid tube 10 it need not be of high strength material and itscomposition can contain relatively large amounts of melamine andhydrated alumina.

The circuit interrupter illustrated in FIG. 2 is formterrupting heavypower circuits. It comprises an outer cylindrical shell 40 of a moldedcomposition selected for its physical strength, lined with a moldedtubular liner 42 of a composition selected for its arcinterruptingcharacteristics. At spaced points along its length, the tubular assemblycarries a pair of contact units each consisting ofa fixed hollow stud 44in which a contact 46is spring pressed inward. For closing a circuitbetween the contacts, the shell assembly 40-52 contains a slidable rod48 which has a relatively close fitting relation in the liner 42. Therod comprises a shorting spool 50 having lands 52 spaced to engagewiththe spring-pressed contacts 46 and having its center portionsurrounded by an insulating sleeve 54 and its ends fixed in end pieces56. The sleeve and end pieces, like the liner 42 are of a compositionhaving arc-interrupting characteristics in accordance with the presentinvention.

When the rod assembly 48 is moved to bring the lands 52 into registrywith the contact members 46, a large-capacity electrical circuit isclosed between the two contacts 46. To open that circuit, the rodassembly is drawn axially to carry the lands 52 out of registry with thecontacts 46. When this is done, the arcs which form between theseparating lands and contacts are drawn between the close fittingsurfaces of the liner 42 and the insulting parts 54 and 56 of the rod,so that the physical confinement of the arcs, and the arcinterruptingcharacteristics of the material in those surfaces cooperate to interruptthe are.

In the test apparatus shown in FIG. 7, the test specimen is molded as atube 160. This is mounted to enclose a fixed electrode 162, and amovable electrode 164 is cyclically moved into arc-striking proximitywith the fixed electrode 162 and withdrawn therefrom to lengthen the arebetween the electrodes. The movable electrode is actuated by amotor-driven constant-rise cam 166 which withdraws the movable electrodeI64 at a constant rate through a stroke of fixed length and thenreleases the electrode for return by a spring 168. The are circuit issupplied with power from a l 10 volt, '60 cycle A.C. circuit 170 and thevoltage is raised by a transformer 172 to 15,000 volts. The electrodecircuit is coupled through a transformer 176 to an oscillograph 174 ofatype which draws a trace of the alternating instantaneous currentwaveform on a paper tape which is advanced as the electrodes are drawnapart. In the recorded waveform, the amplitude of the oscillationsrepresents the current flowing in the arc, and the duration of theoscillations represents the duration of the arc, and shows when thecurrent is interrupted and the arc is extinguished.

EXAMPLE I The test apparatus shown in FIGS. 4 and 5 was used to runtests giving the results shown in FIG. 6. The test apparatus comprises apair of contacts 60 and 62 mounted in a box like housing 64 and arrangedto be closed by a pair of bridging contacts 66 mounted on a cross bar 68operatively connected to a plunger 70 by which the contacts 66 can beraised andlowered into and out of engagement with the contacts 60 and62, to close a circuit between them. In a test setup, the contacts 60and 62 are connected across a 600 volt circuit, and an oscillograph 65is connected across the contacts 60-"62 through a transformer 67. Theoscillograph shows essentially no voltage when the contacts are closed,then as the contacts open the voltage drop across the arc increasesuntil the arc extinguishes and the full voltage is registered across thecontacts. The time the arc continues constitutes a measure of theefficiency of the arc extinguishing characteristics of the apparatus,and the duration of the arc is counted in half-cycles of 60-cyclecurrent.

The housing 64 is a molded body of a conventional high-strength moldingcomposition, of polyethylene resin, glass fiber, and hydrated alumina.Its end wall portions 72 are formed with cavities 74 which are filledwith inserts 75 of different test materials. The bottom of the housingis closed by a bottom wall 76. In the operation of such a switch,magnetic field effects cause the are formed between the contacts to bedeflected outward from between the contacts and hence against theinserts 75 of test material.

In test operatiomthe contacts 66 are closed against the contacts 60 and62 and then opened, once every 10 seconds, and the time required tointerrupt the circuit on opening of such contacts is counted in halfcycles of 60-cycle current. Such test sequence is repeated 50 times foreach test, and the count of half-cyces for the 55 sequences is averagedto give a single test result value. For each composition tested, a 50sequence test was made at different current values, in progressivelyincreasing steps, so that each composition was subjected to a series ofsuch 50 test-cycle tests at progressively increasing current values.

The test results for four compositions are shown in FIG. 6. The fourcompositions, identified as compositions A, B, C, and D, contained thecomponents and the proportions shown in the following table.

In each case, the components of the composition were mixed thoroughlytogether and then hot moldedin the cavities 74 of previously preparedhousings 64.

Composition A, of hydrated alumina and melamineformaldehyde resin, isrepresentative of the hydrated alumina compositions of US. Pat. No.2,768,264. (The melamine-formaldehyde resin used as the binder in thiscomposition is not the same as melamine, the compound in compositionsB-D, but is a thermosetting resin binder which has a strong tendency tocarbonize and does not have the arc interrupting characteristics ofmelamine per se.) Composition A was tested in a series of 50 test-cycletests at progressively increasing current values from 100 amperes to 410amperes. The switch 60-62-66 was opened 50 times at lO-second intervals,the time required for are interruption on each switch opening wascounted in half-cycles, and the 50 counts were averaged. The resultingaverage interruption times for the successive tests are shown by Curve Aon the graph of FIG. 6. The average interruption time was less than 1.1half-cycles on each of the tests at 100, 160., 210, 265, and 320amperes, but on subsequent tests at 365 amperes and 410 amperes the arcinterruption time increased abruptly and Curve A therefore rises steeplyafter the 320 ampere position. The location of this abrupt increase issignificant for comparison with test of other materials.

Composition B comprised three parts each of melamine, polyethylne resinbinder, and silica filler. This composition was discloSed as one of theexamples in our prior co-pending application, and is rere'sentative of anumber of'test compositions consisting essentially of melamine and athermoplastic binder. Again, with composition B, a series of tests weremade on apparatus as shown in FIGS. 4 and 5, at progressively increasingamperages from 100 amperes to 410 amperes. At each ampere value, theswitch contacts wereopened once every seconds for 50 times, and the timerequired for circuit interruption on each such opening observed andcounted in half-cycles. The average interruption time at each amperageis plotted on the graph and shown by Curve B of FIG. 6. With compositionB, the interruption time progressively increased at a moderate rate onthe successive tests at from 100 amperes to 265 amperes and thenincreased rapidly at the subsequent tests at 320, 365, and 410 amperes,so that the Curve B rose sharply for these ampere values.

Compositions C and C embody the present invention. Composition Ccontained three parts each of melamine, polyethylene resin binder, andhydrated alumina, and composition D contained one part melamine, onepart polyethylene resin binder, and four parts hydrated alumina. Thesewere tested in the same manner as Compositions A and B. With both ofthese compositions, the average arc interruption time on 50 switchopenings on each test was only about 1.1 half cycle or less throughoutthe eight successive tests from 100 amperes up to an amperage level of460 amperes, and the arc-interruption time did not sharply increaseuntil after the 460 ampere test.

Thus on these four tests, compositions A and B showed a sharp rise inthe arc-interruption time in successive tests after 320 amperes, whereascompositions C and D in accordance with the present invention gavearc-interruption times averaging only about 1.1 halfcycles or less overa much larger number of successive tests and at much higher amperagelevels.

EXAMPLE II Tests of different compositions were made using apparatus asshown in FIG. 3. Such apparatus consists of a switch blade mounted to beswung about a fixed pivot 82 into and out of engagement with a pair ofcontact jaws 84. The blade was operated by an arm 83 which swung theswitch blade 80 with a snap action between open and closed positions. Apair of arc quenching plates 86 were mounted closely beside the path ofthe blade 80. Such walls 86 were provided with notches 88 at the bottomto clear the switch jaws 84, and the walls extended beyond such jawssufficiently to confine the are which formed betwen the blade and jawsas the switch was opened.

In test operations, the blade 80 was opened from the jaws 84 in a seriesof openings with the walls 86 composed of different test compositions,and observations were made of the efficiency of the wall compositions inextinguishing the are formed between the blade and the aws.

A test was made with walls of a composition E, composed of two partsmelamine and one part polyethylene resin binder. Such components weremixed in dry powder state, and then hot-molded in the form of flatsheets. The walls 86 were cut from such sheets. For this test, theswitch parts were connected to interrupt a circuit at 15 KV and 200amperes. Although composition E in the walls 86 was effective at firstto extinguish the arc, after three or four switch-openings, such walls86 of composition E became so softened and deformed by the heat of theare that they physically interfered with the opening of the switch blade80 and prevented continuation of the test.

Another test was made with the same apparatus using walls of acomposition F consisting of two parts melamine and'one part polyethyleneresin binder (the same as composition E) and one part hydrated alumina.Again, the components were mixed dry and hot molded to form sheets fromwhich the walls were fabricated. With walls 86 of such composition F,the arc was extinguished effectively during continuous repetitions ofswitch openings for more than 300 openings with no noticable softeningor deformation of the walls. Tests were then made with the same walls athigher amperage, namely, at 300 amperes and I5 KV, and the walls of theComposition F were agan effective to extinguish the are formed betweenthe blade 80 and the jaws 84 on a continuous succession of switchopenings, without wall softening or deformation. Tests were then made at22 KV and 200 amperes, and the walls of Composition F were againeffective. Tests were then made at 15 KV and 400 amperes, and the wallsof composition F were again effective to extinguish the arc in acontinuous succession of switch openings. Thus, where composition Efailed by softening and physical deformation within a few test openings,composition F in accordance with the present invention gave effectivearc interruption and maintained its physical integrity throughout anumber of tests with continuously repeated openings, at the same andhigher power conditions, and for a total of several hundred switchopenmgs.

Instead of molding the arc-interrupting compositions in or as the arcconfining walls of electrical apparatus as in FIGS. l5, suchcompositions may also be applied as coatings to selected surfaces ofwalls formed of other material. This is especially suitable for certainclasses of overload circuit breakers, for example, in which effectivearc interruption performance is required but which need to have aservice life of only a few operating cycles.

A paint-like coating suitable for application to the inner walls of thehousing of a circuit breaker of this class may be formulated by firstmixing melamine and hydrated alumina in finely powder state, and thensuspending the mixed powders in a liquid vehicle to form a paintJikecoating material. The liquid vehicle may be a mixture of a binder resinanda solvent, to form a coating material from which the solvent willevaporate to leave a solid coating. Alternatively, the liquid vehiclemay be a mixture of reactive components, such as are known in theformulation of epoxy paints, which will react after application to forma solid coating. By using melamine and hydrated alumina as the solidscontent with such'liquid vehicles, a paint like material is formedwhich, on application to an arc exposure surface, forms a solid coatingthereon having a composition in accordance with the present invention.

EXAMPLE III The test apparatus shown in FIG. 7 was used to determine therange of proportions of the essential components of arc interruptingcompositions. Specimen tubes 160 were molded of different compositionsincluding a binder, different proportions of melamine and hydratedalumina, as shown in the following Table II.-With each specimen, aseries of circuit interruptions were made, and the arc length aridcurrent in each case was recorded in a trace on the tape. The resultingtape records were examined to make sure that uniform arcinterruptingresults were obtained on each composition, and the tape records werethen evaluated to obtain comparative numerical values, as follows:

Arc Length Index is a measure of the length of the are as a percentageof the totalstroke length, and indicates the duration of the arc and itsenergy.

Ampere Index is a measure of the amplitude of the current waveform justbefore the arc is extinguished and represents the current then flowingin the arc in comparison with the full amperage (30 ma) of the circuit.A lower Ampere Index indicates attenuation of the current waveform, andshows greater deionization and reduced conductivity in the arc path, andgreater quenching produced by the composition being tested. EnergyProduct is the mathematical product of the Arc Length Index and theAmpere Index, and is a comparative representation of the energy expendedin the arc.

These values are not given as accurate quantitative measurements, butare considered to be representative for purposes of comparison.

In the following Table II, the first three columns rep resent thepercentage proportions of melamine, hydrated alumina and binder in thecomposition tested. The same binder was used in all compositions. Thecompositions are arranged in the decreasing order of the proportions ofmelamine to hydrated alumina. The last three columns show the resultsobtained, in terms of the three values explained above.

For correlation with previous test results, Table II also includescompositions of Examples I and II. Thus, I-A, I-C, and 1-D respectivelyrepresent compositions A, C and D of Example I above, and [HE and ll-Frepresent compositions E and F of Example II. (Composition A of ExampleI used a different binder than that tested in this Example III, but hadthe same proportions.)

TABLE II Arc Mcln- Hydrated longtli Ampere Energy IIIIIlI alumina Binderindm indvx product 0 10 8G. I 27 23 80 U .30 8t. .38 '35 II-II 66% ll33% 86.1 30 '26 77. 2. 5 2O 80 15 113 75 5 20 70. U 15 12! TL. 5 7. 5 20G7. 7 10 7 70 10 .20 7 10 T 61 l 30 80 1'2 52. 5 7. 5 4O 80 12 10 I [-F50 25 25 II-I 50 30 81. 5 '20 48. 8 26. l 73. 8 15 11 37. 5 22. 5 40 73.8 l5 I1 45 8O 17 22 I-C 33% 33%.; I4,

30 3U 15 ll .25 .25 I0 7. 4 30 35 2O 26. 2 43. 8 .20 17 22 37 ,2 20 16II) 16% 66% I-I 10 T0 20 81. 5 37 2'2 I-A* 0 R5 15 No interruption U66%;; 33% No interruption Composition IA (Rosita 2150) contained adifferent hinder, but had the same proportions.

Table II shows that dramatic improvements are obtained by addinghydrated alumina to a melamine composition and by adding melamine to ahydrated alumina composition.

a. At thetop of the table, the first three compositions contain melamineand binder but no hydrated alumina. While they were effective toextinguish the arc, they gave high Arc Length Indexes of from 86.l to89.2 percent of the total stroke length, and gave high Ampere Indexes.The Energy Product in each case is correspondingly high. The next fourcompositions represent the addition of small proportions of hydratedalumina to melamine compositions, and produce a dramatic and surprisingimprovement. They greatly reduce the arc length, the current, and theenergy product.

b. At the bottom of the table, the bottom two compo sitions containhydrated alumina and binder but no melamine. These alumina-alonecompositions each failed to interrupt the are under the test conditions.A dramatic improvement was obtained by using small percentages ofmelamine in combination with the hydrated alumina. The three-componentcompositions, instead of failing, were operative to interrupt the arc.They gave shorter arcs than the three melamine-alone compositions at thetop of the table, gave substantially reduced Ampere Indexes, and gavereduced Energy Products.

c. Throughout Table II, all compositions containing both melamine andhydrated alumina showed improved results over compositions containingeither melamine alone or hydrated alumina alone.

The test results show that improved results are obtained by thecombination of both melamine and hydrated alumina in a binder, and thatthe improved results are obtained over a wide range of proportions. Theyshow that for each 100 parts of the three essential components, thebinder is effective if present in the proportion of from 10 to 50 parts.They show that me]- amine is effective if present in an amount of atleast 10 parts and up to very high proportions limited only by thenecessity for a small proportion of hydrated alumina. They show thathydrated alumina is effective if present in amounts up to 70 parts outof the 100 total, and that it is especially effective in very smallamounts, down to 1 part per 100 or less. Good results were obtained withonly 2.5 parts and the best test results were obtained with hydratedalumina present in amounts of 5 to parts.

The test results of this Example III correlate with the test resultspreviously reported. Thus the 85 percent hydrated alumina, percentbinder composition failed here, and the corresponding composition A ofExample I have poor results on lower voltage tests, and the melaminecomposition lI-E permitted long high energy arcing here and the samecomposition was destroyed by heat in the tests of Example ll. Also,Compositions I-D and I-C of the present example are in the range wherebetter results were obtained in this Example III, and those compositionsalso gave better results in the tests of Example I and FIG. 6. Also,Composition II-F is in the range where better results were obtained thanwith composition "-5, just as was the case in Example II.

I claim:

1. A new are interrupting composition consisting cssentially ofmelamine, hydrated alumina, and a binder, each 100 parts by weight ofsaid components containing binder in an amount from 10 parts to 50parts, melamine in an amount of at least 10 parts, and hydrated aluminain an amount in the range of from about 1 part up to about parts.

2. An arc interrupting composition as in claim 1 wherein the binder is athermoplastic resin.

3. An arc interrupting composition as in claim 1 wherein the binder is apolyethylene resin.

4. An arc interrupting component for an electrical circuit interrupter,comrising a molded body defining an arc exposure surface and composed atsuch surface of an arc-interrupting composition as defined in claim 1.

5. An electrical circuit interrupting device, comprising an insulatingbody defining a surface across which an electric arc can occur, andcomposed at such surface of an arc-interrupting composition as definedin claim 1.

6. An arc interrupting device as in claim 5 in which saidarc-interrupting composition is present as a surface layer on aninsulating body of other composition.

UNKTED STATES ?ATENT @FFICE CERTIFICATE OF CORRECTION Patent No.3,761,660 Dated September 25, 1223 Inventofls) Paul W. Jones I It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 2, line 34, change "compunned" to --compound-.

Col. line 42, change "40-62" to "40-42".

Col. line 60,, change "insulting" to --insulating--.

Col. line 57; change "half-cyces" to --half-cycles--.

Col, line 41, change "disclosed" to "disclosed".

Col.

Col; 6, line 58 change "55" to --50-- 7 line 42, change "reresentative"to "representative-m Col. line 59, change "C and C" to --C and D--001.10, in Table II, coluinn entitled Melamine, change the 12th numberdown from the top from"'48 .8" to -43.8--.

001.12, line 17 change "comrising" to "comprising".

Signed and sealed this 19th day of March 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR, c. MARSHALL DANN Attesting Officer ICommis'sionerof Patents 1 FORM ($69) 7 uscoMM-oc wave-pea \J.S.GOVERNMENT PRINT NG OFFICE 1 l9! 0-366!!! UNITED STATES PATENT OFFICEQERTEFECATE F CORRECTION Patent No 3 761 660 Dated Sggtgmbgr 223Inventor(s) Paul W. Jones It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. 2, line 34, change "compunned" to --compound--.

Col. line 42, change "-52" to 40-42-.

COL. line 57, change "half-cyces" to --half-cycles-.

C01. line 41, change "disclosed" to --disclosed--.

, line 42, change "reresentative" to -r epresentative--.

Col; 6, line' 58 change to --50--.

Col. 7

Col. line 59, change "C and C" to --C and D 001.10, in Table II, columnentitled Melamine, change the 12th number down from the top from "48 .8"to "43 .8-

Col.l2, line 17 change "comrising" to --comprising--.

Signed and sealed this 19th day of March 1974.

(SEAL) Attest:

EDWARD M. FLETCHER, JR. (3. MARSHALL DANN Attesting Officer 1Commissioner'of Patents "ORM PO-O (10-69) USCOMM'DC 60376-P69 i \LS.GOVERNMENT PRINTING OFFICE: l9! O-366-3I4 N

1. A new arc interrupting composition consisting essentially ofmelamine, hydrated alumina, and a binder, each 100 parts by weight ofsaid components containing binder in an amount from 10 parts to 50parts, melamine in an amount of at least 10 parts, and hydrated aluminain an amount in the range of from about 1 part up to about 70 parts. 2.An arc interrupting composition as in claim 1 wherein the binder is athermoplastic resin.
 3. An arc interrupting composition as in claim 1wherein the binder is a polyethylene resin.
 4. An arc interruptingcomponent for an electrical circuit interrupter, comrising a molded bodydefining an arc exposure surface and composed at such surface of anarc-interrupting composition as defined in claim
 1. 5. An electricalcircuit interrupting device, comprising an insulating body defining asurface across which an electric arc can occur, and composed at suchsurface of an arc-interrupting composition as defined in claim
 1. 6. Anarc interrupting device as in claim 5 in which said arc-interruptingcomposition is present as a surface layer on an insulating body of othercomposition.